1. Field of the Invention
The present invention relates to a surface resolution calibration method utilized in an optical image system, and in particular to a calibration method that can be used to correct the image magnification factor of the corresponding pixel.
2. The Prior Arts
In the prior art, the optical image system surface resolution calibration method is used by the imaging device for calibration, thus the magnification factor of images produced by the pixel of CCD sensor or CMOS sensor is determined. Usually, this kind of technology is realized through a scaled image having size indication produced by an imaging device. Referring to FIG. 7 for a schematic diagram for the implementation of surface resolution calibration method used in the optical image system of the prior art. As shown in FIG. 7, the positions P1 and P2 on the scale are determined manually or by an image processing method, and these positions are used to calculate the distance between the two pixels corresponding to the two positions P1 and P2 on the scale. Since the actual distance between the positions P1 and P2 on the scale 6 is determined by design, thus the actual size of the object to be measured that corresponds to the positions of the pixels of the optical image system can be obtained by comparing the size of the actual distance and the distance between the two pixels. However, in the implementation of this technology, the disposition of the scale must reach the horizontal axis paralleling to the horizontal axis as determined by the pixels of the imaging device, and if there exists an inclination angle between the scale and the horizontal axis, then the measured result will be shorter than the actual size of the object to be measured, as such producing linear deviation. Therefore, the scale used in the optical image system surface resolution calibration method of the prior art must be utilized in cooperation with a revolving table to adjust the parallelism of the scale, hereby increasing the complexity of the mechanism of the optical image system, and adversely affecting the accuracy and speed of the calibration.
Therefore, the research and development of an optical image system surface resolution calibration method and device that can be used to raise the accuracy and speed of the calibration and simplify its complexity, is the most important task in this field.